Key result
Deletion of the 11 amino acids preceding the C-terminal tail (Delta414-424) of Kir2.1 completely disrupts binding to PSD95 PDZ1,2, indicating regions outside the SEI428 motif are involved.
The molecular interfaces between PDZ domains and the Kir2.1 tail involve regions outside the previously identified binding motif, which may be important for channel-specific interactions.
Regions outside the SEI428 motif mediate Kir2.1-PSD95 binding; leaves open their role in cardiac channel regulation.
Control of surface expression of inwardly rectifying potassium (Kir) channels is important for regulating membrane excitability. Kir2 channels have been shown to interact directly with PDZ-containing proteins in the postsynaptic density (PSD). These scaffold proteins, such as PSD95, bind to Kir2.1 channels via a PDZ-binding motif (T/S-x-Phi) in the C-terminal tail (SEI428). By utilizing a multidimensional solution NMR approach, we show that the previously unresolved structure of Kir2.1 tail (residues 372-428) is highly flexible. Using in vitro binding assays, we determined that shortening the flexible tail of Kir2.1 preceding the C-terminal region (residues 414-428) does not significantly disrupt PDZ binding. We also investigated which amino acids in the Kir2.1 tail associated with PSD95 PDZ1,2 by NMR spectroscopy, revealing that a stretch of 12 C-terminal amino acids is involved in interaction with both PDZ domains (residues 417-428). Deletion of the 11 amino acids preceding the C-terminal tail, Delta414-424, completely disrupts binding to PSD95 PDZ1,2. Therefore, the molecular interfaces formed between PDZ domains and Kir2.1 tail involve regions outside the previously identified binding motif (SEI428) and may be important for additional channel-specific interactions with associating PDZ-containing proteins.
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Pegan et al. (2007) studied this question. Deletion of 11 amino acids preceding the C-terminal tail (Delta414-424) was evaluated on Binding to PSD95 PDZ1,2. Deletion of the 11 amino acids preceding the C-terminal tail (Delta414-424) of Kir2.1 completely disrupts binding to PSD95 PDZ1,2, indicating regions outside the SEI428 motif are involved.
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